1. Field of the Invention
The present invention relates to imidazole derivatives, and particularly to novel imidazole derivatives and salts thereof, which combine an excellent suppressive effect on the production of cytokine with high safety and are useful as medicines such as immune function modulators.
2. Description of the Background Art
An immune system inherent in the viable body, which is a protective mechanism against extrinsic or intrinsic foreign bodies, consists of a cell group of the monocytic series, typified by a macrophage and a neutrophil, and a cell group of the lymphocytic series composed of a T cell and a B cell. These cell groups not only separately function, but also maintain the homeostasis by direct contact between the cells or interaction through a soluble factor generally designated cytokine. The mechanism thereof is minute in the extreme, and a subtle breakdown of the balance induces a serious morbid state.
For example, a collagen disease, systemic lapus erythematosus, and various allergic diseases are said to be caused as a result that the regulatory mechanism of such immunocytes is broken down, whereby autoantibodies are produced, and an excess immune reaction is induced. In AIDS (acquired immunodeficiency syndrome), it is also known that the immune mechanism is broken down by infecting a T cell with HIV, and its morbid state is allowed to progress. It has also been definitely shown that the breakdown of the balance in the immune system forms a cause that the morbid states of diabetes, viral chronic diseases and cancer are allowed to progress.
In recent years, cytokine-production suppressors such as cyclosporin and FK506 already known as rejection suppressors upon organ transplantation have been used for diseases caused as a result of an excess immune reaction. Besides, anti-inflammatory steroid agents having a cytokine-production suppressing effect have also been used for autoimmune diseases such as allergy, atopy and rheumatism, and bronchial asthma, and some therapeutic effect has been achieved.
However, these immunosuppressive agents and anti-inflammatory steroid agents are such that the production of many kinds of cytokine is suppressed. Therefore, the administration of such an agent to a patient suffering from an autoimmune disease in particular has required to take measures such as the limitation of an administration method and the administration of the agent with an intermission from the viewpoint of safety.